CHAPTER XII.
ODDS AND ENDS.
MINER'S INCH.
A miner's inch of water varies in different States, and is, therefore, not a fixed quantity. In some States it means the quantity of water that will flow through an orifice one inch square on the bottom or side of a box under a pressure of four inches. Under these conditions a miner's inch will discharge 2259 cubic feet, or 17,648 gallons every twenty-four hours, which is at the rate of 12 gallons a minute. Fifty of these miner's inches are equal to a cubic foot of water discharged every second. One cubic foot of water a second would be sufficient to supply the wants of seven thousand city dwellers.
In calculating the amount of water required by a stamp mill it is usual to allow 72 gallons for every stamp, 120 gallons for every pan, 75 gallons for every settler, 120 gallons for every Fruevanner, 30 gallons for a concentrator, 350 gallons for a jig, and 7½ gallons for every horse-power of a boiler each hour. If the water after passing through the mill is impounded and used over again, the loss will be about 25 per cent.
LUMBER IN A LOG.
To Find: Multiply the diameter in inches at the small end by one-half the number of inches, and again multiply this product by the length of the log in feet; this product divided by 12 will give the number of feet of one-inch boards the log will make.
HORSE-POWER OF BOILERS.
For horizontal, tubular and flue boilers, divide the number of feet of heating surface by 15; this will give the horse-power. A cord of pine wood weighing 2,000 pounds is about equal to 1,000 pounds of soft coal for steam purposes. Each foot of grate should burn 20 pounds of soft coal, or 40 of wood, per hour, with a natural draught.
HORSE-POWER OF AN ENGINE.
Multiply the area of the cylinder in square inches by the average effective pressure in pounds to the square inch, deducting three pounds per square inch for friction. Multiply this remainder by the speed of the piston in feet per minute, and divide by 33,000. The quotient will be the true horse-power.